Zoom lens system, imaging device and camera

ABSTRACT

A zoom lens system comprising a plurality of lens units each composed of at least one lens element, wherein an interval between at least any two lens units among the lens units is changed so that an optical image of an object is formed with a continuously variable magnification, a first lens unit arranged on the most object side among the lens units includes a lens element having a reflecting surface for bending a light beam from the object, and any one of the lens units, any one of the lens elements, or alternatively a plurality of adjacent lens elements that constitute one lens unit move in a direction perpendicular to an optical axis; an imaging device including the zoom lens system; and a camera employing the imaging device.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Divisional of U.S. application Ser. No.11/600,066, filed Nov. 16, 2006, now U.S. Pat. No. 7,471,453 issued onDec. 30, 2008 and claims priority of Japanese Application No.2005-333161 filed in Japan on Nov. 17, 2005, the entire contents of eachof which are hereby incorporated by reference.

BACKGROUND

1. Technical Field

The present invention relates to a zoom lens system, an imaging deviceand a camera. In particular, the present invention relates to: a zoomlens system that is used suitably in a small and high-image qualitycamera such as a digital still camera or a digital video camera, hencehas high resolution, and has a blur compensation function of opticallycompensating blur caused in an image by hand blur, vibration or thelike; an imaging device including this zoom lens system; and a thincompact camera employing this imaging device.

2. Description of the Background Art

With recent progress in the development of solid-state image sensorssuch as a CCD (Charge Coupled Device) and a CMOS (ComplementaryMetal-Oxide Semiconductor) having a high pixel, digital still camerasand digital video cameras are rapidly spreading that employ an imagingdevice including an imaging optical system of high optical performancecorresponding to the above solid-state image sensors of a high pixel.

Among these, especially in digital still cameras, thin constructionshave recently been proposed in order to achieve satisfactoryaccommodation property or portability to which the highest priority isimparted. As possible means for realizing such thin digital stillcameras, a large number of zoom lens systems for bending a light beam aswell as lens barrels and imaging devices employing these systems havebeen proposed.

For example, Japanese Laid-Open Patent Publication No. H11-258678discloses a lens barrel comprising: a fixed first stage shooting lens; aplurality of movable shooting lens units arranged in the subsequentstages of the shooting lens; optical axis changing means in the middleof the plurality of movable shooting lens units; and driving means formoving in the shooting optical axis direction the movable shootinglenses located upstream and downstream the optical axis changing means.In this lens barrel disclosed in Japanese Laid-Open Patent PublicationNo. H11-258678, since the optical axis changing means is arranged in themiddle of the plurality of movable shooting lens units, the interval isreduced between the shooting lens of the first stage and the movableshooting lens units of the subsequent stages. This reduces the diameterin the shooting lens of the first stage, and hence reduces the volume ofthe entire lens barrel.

Further, Japanese Laid-Open Patent Publication No. H11-196303 disclosesan electronic imaging device comprising a shooting lens unit that has aplurality of lenses and optical axis changing means arranged between theplurality of lenses and that is arranged on the frontward of thephotographic object side of an image display section provided in a rearface of a main body of the device, so that object light having passedthrough the shooting lens unit is photoelectrically converted andrecorded by an image sensor. In this electronic imaging device disclosedin Japanese Laid-Open Patent Publication No. H11-196303, since theshooting lens unit is provided with the optical axis changing meansarranged between the lenses, a construction is formed that the lightbeam is bent in the middle. Further, the image display section isarranged in the rear face. This avoids the main body of the devicebecomes thick, and realizes a shape of satisfactory balance where thehorizontal dimension is reduced.

Furthermore, Japanese Laid-Open Patent Publication No. 2004-354869discloses a zoom lens system that has a five-unit construction ofpositive, negative, positive, positive and negative in order from theobject side, and that performs zooming by moving a second lens unit anda fourth lens unit, in which a first lens unit, in order from the objectside, comprises a negative front side lens unit, an optical member forbending an optical path, and a positive rear side lens unit, and inwhich the imaging magnification of a fifth lens unit is set within aspecific range. In this zoom lens system disclosed in Japanese Laid-OpenPatent Publication No. 2004-354869, since the first lens unit comprisesthe negative front side lens unit, the optical member for bending theoptical path, and the positive rear side lens unit, the moving directionof the second lens unit and the fourth lens unit at the time of zoomingaligns with the optical axis direction of the rear side lens unit of thefirst lens unit. This reduces the thickness of the lens system. Further,since the imaging magnification of the fifth lens unit is larger than aspecific value, the focal length is reduced in the lenses arranged onthe object side thereof. This reduces the overall length of the lenssystem, and reduces the effective diameter in the front side lens unitand the rear side lens unit of the first lens unit.

Nevertheless, in the lens barrel disclosed in Japanese Laid-Open PatentPublication No. H11-258678, the shooting lens unit that moves in theoptical axis direction in zooming is included between the shooting lensof the first stage located on the most object side and the optical axischanging means. Thus, the entire lens barrel is not sufficientlysize-reduced. Further, the zoom lens system itself held by the lensbarrel is not specified sufficiently, and hence this zoom lens systemdoes not seem to correspond to blur compensation.

Similarly, in the electronic imaging device disclosed in JapaneseLaid-Open Patent Publication No. H11-196303, the shooting lens unititself is not specified sufficiently, and hence this electronic imagingdevice does not seem to have a sufficient blur compensation function.Further, the lens eyepiece part and the release switch are far apartfrom each other. This construction easily causes blur in the image owingto hand blur.

Further, in the zoom lens system disclosed in Japanese Laid-Open PatentPublication No. 2004-354869, a specific lens system having a five-unitconstruction is employed so that thickness reduction is achievedreliably while the overall length is reduced in the lens system.Nevertheless, its blur compensation function is not satisfactory, andhas a problem that sufficient optical performance cannot be maintainedwhen blur compensation is performed.

SUMMARY

The present invention has been made in order to resolve the problems inthe prior art. An object of the present invention is to provide: a zoomlens system that has a short overall length and hence is thin andcompact, that has high resolution, and that has a blur compensationfunction of optically compensating blur caused in an image by hand blur,vibration or the like; an imaging device including this zoom lenssystem; and a camera employing this imaging device.

The novel concepts disclosed herein were achieved in order to solve theforegoing problems in the conventional art, and herein is disclosed:

a zoom lens system comprising

a plurality of lens units each composed of at least one lens element,wherein

an interval between at least any two lens units among the lens units ischanged so that an optical image of an object is formed with acontinuously variable magnification,

a first lens unit arranged on the most object side among the lens unitsincludes a lens element having a reflecting surface for bending a lightbeam from the object, and

any one of the lens units, any one of the lens elements, oralternatively a plurality of adjacent lens elements that constitute onelens unit move in a direction perpendicular to an optical axis.

The novel concepts disclosed herein were achieved in order to solve theforegoing problems in the conventional art, and herein is disclosed:

an imaging device capable of outputting an optical image of an object asan electric image signal, comprising

a zoom lens system that forms the optical image of the object and

an image sensor that converts the optical image formed by the zoom lenssystem into the electric image signal, wherein

the zoom lens system comprises a plurality of lens units each composedof at least one lens element, in which

an interval between at least any two lens units among the lens units ischanged so that an optical image of an object is formed with acontinuously variable magnification,

a first lens unit arranged on the most object side among the lens unitsincludes a lens element having a reflecting surface for bending a lightbeam from the object, and

any one of the lens units, any one of the lens elements, oralternatively a plurality of adjacent lens elements that constitute onelens unit move in a direction perpendicular to an optical axis.

The novel concepts disclosed herein were achieved in order to solve theforegoing problems in the conventional art, and herein is disclosed:

a camera for converting an optical image of an object into an electricimage signal and then performing at least one of displaying and storingof the converted image signal, comprising

an imaging device including a zoom lens system that forms the opticalimage of the object and an image sensor that converts the optical imageformed by the zoom lens system into the electric image signal, wherein

the zoom lens system comprises a plurality of lens units each composedof at least one lens element, in which

an interval between at least any two lens units among the lens units ischanged so that an optical image of an object is formed with acontinuously variable magnification,

a first lens unit arranged on the most object side among the lens unitsincludes a lens element having a reflecting surface for bending a lightbeam from the object, and

any one of the lens units, any one of the lens elements, oralternatively a plurality of adjacent lens elements that constitute onelens unit move in a direction perpendicular to an optical axis.

The present invention provides a zoom lens system that has a shortoverall length and hence is thin and compact, that has high resolution,and that has a blur compensation function of optically compensating blurcaused in an image by hand blur, vibration or the like. Further, thepresent invention provides: a thin imaging device that includes thiszoom lens system and that has high resolution and a blur compensationfunction; and a camera that employs this imaging device and that has ashort startup time, dustproof and waterproof properties, and a notablyreduced longitudinal dimension.

BRIEF DESCRIPTION OF THE DRAWINGS

This and other objects and features of this invention will become clearfrom the following description, taken in conjunction with the preferredembodiments with reference to the accompanied drawings in which:

FIG. 1 is a transparent perspective view showing an outlineconfiguration in an imaging state of a camera employing an imagingdevice according to Embodiment 1;

FIGS. 2A to 2C are lens arrangement diagrams showing a zoom lens systemaccording to Embodiment 3 (Example 1) in an infinity in-focus conditionat a wide-angle limit, a middle position and a telephoto limit;

FIGS. 3A to 3I are longitudinal aberration diagrams of a zoom lenssystem according to Example 1 in an infinity in-focus condition at awide-angle limit, a middle position and a telephoto limit;

FIGS. 4A to 4F are lateral aberration diagrams of a zoom lens systemaccording to Example 1 at a telephoto limit;

FIGS. 5A to 5C are lens arrangement diagrams showing a zoom lens systemaccording to Embodiment 4 (Example 2) in an infinity in-focus conditionat a wide-angle limit, a middle position and a telephoto limit;

FIGS. 6A to 6I are longitudinal aberration diagrams of a zoom lenssystem according to Example 2 in an infinity in-focus condition at awide-angle limit, a middle position and a telephoto limit;

FIGS. 7A to 7F are lateral aberration diagrams of a zoom lens systemaccording to Example 2 at a telephoto limit;

FIGS. 8A to 8C are lens arrangement diagrams showing a zoom lens systemaccording to Embodiment 5 (Example 3) in an infinity in-focus conditionat a wide-angle limit, a middle position and a telephoto limit;

FIGS. 9A to 9I are longitudinal aberration diagrams of a zoom lenssystem according to Example 3 in an infinity in-focus condition at awide-angle limit, a middle position and a telephoto limit;

FIGS. 10A to 10F are lateral aberration diagrams of a zoom lens systemaccording to Example 3 at a telephoto limit;

FIGS. 11A to 11C are lens arrangement diagrams showing a zoom lenssystem according to Embodiment 6 (Example 4) in an infinity in-focuscondition at a wide-angle limit, a middle position and a telephotolimit;

FIGS. 12A to 12I are longitudinal aberration diagrams of a zoom lenssystem according to Example 4 in an infinity in-focus condition at awide-angle limit, a middle position and a telephoto limit;

FIGS. 13A to 13F are lateral aberration diagrams of a zoom lens systemaccording to Example 4 at a telephoto limit;

FIGS. 14A to 14C are lens arrangement diagrams showing a zoom lenssystem according to Embodiment 7 (Example 5) in an infinity in-focuscondition at a wide-angle limit, a middle position and a telephotolimit;

FIGS. 15A to 15I are longitudinal aberration diagrams of a zoom lenssystem according to Example 5 in an infinity in-focus condition at awide-angle limit, a middle position and a telephoto limit; and

FIGS. 16A to 16F are lateral aberration diagrams of a zoom lens systemaccording to Example 5 at a telephoto limit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1

First, in the present Embodiment 1, an outline configuration of a camerais described below that employs an imaging device comprising: a zoomlens system that forms an optical image of an object; and an imagesensor that converts into an electric image signal the optical imageformed by the zoom lens system.

FIG. 1 is a transparent perspective view showing an outlineconfiguration in the imaging state of a camera employing the imagingdevice according to Embodiment 1. Here, FIG. 1 is a drawingschematically showing an imaging device according to Embodiment 1. Thus,the scale and the detailed layout can differ from actual ones. In FIG.1, a camera employing an imaging device according to Embodiment 1comprises: a body 1; an image sensor 2; a shutter button 3; a first lensunit 4 that includes a lens element 5 having a reflecting surface 5 aand that is arranged on the most object side; and an image side lensunit 6 arranged on the image side relative to the first lens unit 4.Among these, the first lens unit 4 and the image side lens unit 6constitute a zoom lens system, and thereby form an optical image of anobject in a light acceptance surface of the image sensor 2. Among these,the zoom lens system is held by a lens holding barrel in a lens barrel,while the zoom lens system held by the lens holding barrel and the imagesensor 2 constitute an imaging device. Thus, the camera comprises: thebody 1; and the imaging device constructed from the zoom lens system andthe image sensor 2.

In an imaging state of the camera according to Embodiment 1, the imagesensor 2 is an image sensor such as a CCD or a CMOS, and generates andoutputs an electric image signal on the basis of the optical imageformed in the light acceptance surface by the zoom lens system. Theshutter button 3 is arranged on the upper face of the body 1, anddetermines the acquisition timing for an image signal of the imagesensor 2 when operated by an operator. The lens element 5 has areflecting surface for bending the light beam from the object, that is,a reflecting surface 5 a for bending by approximately 90° the opticalaxis AX1 of the first lens unit 4 (an axial principal ray from theobject), and thereby deflects the object light exiting from the firstlens unit 4 toward the image side lens unit 6. The image side lens unit6 is arranged on the optical axis AX2, and thereby transmits to theimage sensor 2 the object light deflected by the reflecting surface 5 a.

In the zoom lens system employed in the camera according to Embodiment1, a lens element 5 having a reflecting surface 5 a is included in thefirst lens unit 4 so that the light beam from the object is bent by thereflecting surface 5 a. Thus, in an imaging state, the zoom lens systemcan be constructed thin in the optical axis direction of the axial lightbeam from the object. Accordingly, for example, in the case of a zoomlens system having a variable overall length, an accommodated state isrealized approximately in the imaging state at the wide-angle limitwithout the necessity that the first lens unit that includes the lenselement having a reflecting surface and at least one image side lensunit should be moved and escaped from the position of imaging state.Further, for example, in the case of a zoom lens system having a fixedoverall length, an accommodated state is realized in a state near theimaging state at the wide-angle limit.

The lens barrel accommodating the zoom lens system according toEmbodiment 1 comprises in general: a main body; a first lens unitholding barrel; holding barrels each holding at least one image sidelens unit; and guide shafts. In the imaging state, in the inside of themain body, all constructions of the imaging device are held and arrangedin respective holding barrels. In the accommodated state, all theconstructions of the imaging device are accommodated intact inside themain body.

When the zoom lens system according to Embodiment 1 is in the imagingstate at the telephoto limit, the first lens unit holding barrel and theholding barrels each holding at least one image side lens unit arearranged respectively at predetermined positions on the optical axis ofthe light beam (a reflected object light, hereinafter) from the objectbent by the reflecting surface at the telephoto limit.

When the zoom lens system according to Embodiment 1 transits from theimaging state at the telephoto limit to the imaging state at thewide-angle limit, each holding barrel that holds each image side lensunit moves along the optical axis of the reflected object light withbeing guided by the guide shafts, and then stops at each predeterminedposition on the optical axis of the reflected object light at thewide-angle limit. Preferably, the first lens unit holding barrel isfixed during this time. Then, as described above, for example, in thecase of a zoom lens system having a variable overall length, the imagingstate at the wide-angle limit, that is, a state that the intervalbetween the first lens unit and the second lens unit that is arrangedimmediately on the image side of the first lens unit is approximatelythe minimum, may be adopted as an accommodated state. Further, forexample, in the case of a zoom lens system having a fixed overalllength, a state near this imaging state at the wide-angle limit, thatis, a state that the interval between the first lens unit and the secondlens unit that is arranged immediately on the image side of the firstlens unit is near the minimum, may be adopted as an accommodated state.

In contrast, when the zoom lens system according to Embodiment 1transits from the imaging state at the wide-angle limit to the imagingstate at the telephoto limit, each holding barrel that holds each imageside lens unit moves along the optical axis of the reflected objectlight with being guided by the guide shafts, and then stops at eachpredetermined position on the optical axis of the reflected object lightat the telephoto limit. Similarly, preferably, the first lens unitholding barrel is fixed during this time. Then, the holding barrels stopat a position where the interval between the first lens unit and thesecond lens unit arranged immediately on the image side of the firstlens unit becomes the maximum, so that the imaging state at thetelephoto limit is realized.

As such, in the zoom lens system according to Embodiment 1, a lenselement having a reflecting surface for bending the light beam from theobject, that is, a reflecting surface for bending by approximately 90°the axial principal ray from the object, is included in the first lensunit arranged on the most object side. Thus, in the imaging state, thezoom lens system can be constructed thin in the optical axis directionof the axial light beam from the object. This realizes thicknessreduction in the imaging device and the camera.

Here, the embodiment of the above lens element having a reflectingsurface is not limited to a specific one. The lens element having areflecting surface may be any one of: a surface reflection prism; aninternal reflection mirror having a parallel plate shape; and a surfacereflection mirror having a parallel plate shape. However, a prism or amirror having optical power is preferred in particular. Further, thereflecting surface may be fabricated by any one of known methodsincluding: vapor deposition of metal such as aluminum; and forming of adielectric multilayer film. Further, the reflecting surface need nothave a reflectance of 100%. Thus, the reflectance may be appropriatelyadjusted when light for photometry or for an optical finder system needbe extracted from the object light, or alternatively when the reflectingsurface is used as part of an optical path for projecting auto-focusingauxiliary light or the like through itself.

Further, the configuration of the first lens unit is not limited to aspecific one, as long as a lens element having a reflecting surface isincluded. However, preferably, for example, the first lens unit, inorder from the object side to the image side, comprises: a lens elementhaving negative optical power; a lens element having a reflectingsurface; and subsequent lens elements including at least one lenselement and having positive optical power.

Embodiment 2

An imaging device according to Embodiment 2 is the same as the imagingdevice according to Embodiment 1. However, the arrangement directionlayout of the optical axis of reflected object light is different at thetime of arranging in a camera. That is, a camera employing the imagingdevice according to Embodiment 1 adopts a layout that the optical axisof reflected object light is arranged perpendicular to the strokedirection of the shutter button while the imaging device is arrangedhorizontally. In contrast, the camera employing the imaging deviceaccording to Embodiment 2 adopts a layout that the optical axis ofreflected object light is arranged in parallel to the stroke directionof the shutter button while the imaging device is arranged vertically.

As such, in the imaging device according to Embodiment 2, arrangementflexibility is increased when the imaging device is applied to thecamera, and so is the flexibility in designing of a camera.

Here, also in the lens barrel employed in the imaging device accordingto Embodiment 2, similarly to the lens barrel employed in the imagingdevice according to Embodiment 1, for example, in the case of a zoomlens system having a variable overall length, transition is performedfrom the imaging state at the telephoto limit to the imaging state atthe wide-angle limit, so that this imaging state at the wide-anglelimit, that is, a state that the interval between the first lens unitand the second lens unit that is arranged immediately on the image sideof the first lens unit is approximately the minimum, may be adopted asan accommodated state. Further, for example, in the case of a zoom lenssystem having a fixed overall length, a state near this imaging state atthe wide-angle limit, that is, a state that the interval between thefirst lens unit and the second lens unit that is arranged immediately onthe image side of the first lens unit is near the minimum, may beadopted as an accommodated state.

Embodiments 3 to 7

The zoom lens system applicable to the imaging device of Embodiments 1and 2 is described below in further detail with reference to thedrawings. FIGS. 2A to 2C are lens arrangement diagrams of a zoom lenssystem according to Embodiment 3. FIGS. 5A to 5C are lens arrangementdiagrams of a zoom lens system according to Embodiment 4. FIGS. 8A to 8Care lens arrangement diagrams of a zoom lens system according toEmbodiment 5. FIGS. 11A to 11C are lens arrangement diagrams of a zoomlens system according to Embodiment 6. FIGS. 14A to 14C are lensarrangement diagrams of a zoom lens system according to Embodiment 7.FIGS. 2A, 5A, 8A, 11A and 14A show the lens construction at thewide-angle limit (the shortest focal length condition: focal lengthf_(w)). FIGS. 2B, 5B, 8B, 11B and 14B show the lens construction at themiddle position (the middle focal length condition: focal lengthf_(M)=√{square root over ( )}(f_(W)*f_(T))). FIGS. 2C, 5C, 8C, 11C and14C show the lens construction at the telephoto limit (the longest focallength condition: focal length f_(T)).

Each zoom lens system according to Embodiments 3 to 6, in order from theobject side to the image side, comprises: a first lens unit G1 havingpositive optical power; a second lens unit G2 having negative opticalpower; a diaphragm A; a third lens unit G3 having positive opticalpower; and a fourth lens unit G4 having positive optical power. Further,the zoom lens system according to Embodiment 7, in order from the objectside to the image side, comprises: a first lens unit G1 having negativeoptical power; a diaphragm A; a second lens unit G2 having positiveoptical power; and a third lens unit G3 having positive optical power.

Here, a second lens element L2 in each embodiment corresponds to thelens element having a reflecting surface. In the description, theposition of the reflecting surface is omitted. Further, in each of FIGS.2A to 2C, 5A to 5C, 8A to 8C, 11A to 11C, and 14A to 14C, a straightline drawn on the rightmost side indicates the position of an imagesurface S. On its object side, a plane parallel plate P such as anoptical low-pass filter, a face plate of an image sensor or the like isprovided. In the zoom lens system according to Embodiments 3 to 7, theselens units are arranged in a desired optical power construction, so thatsize reduction is achieved in the entire lens system in a state thathigh optical performance is satisfied.

As shown in FIGS. 2A to 2C, in the zoom lens system according toEmbodiment 3, the first lens unit G1, in order from the object side tothe image side, comprises: a negative meniscus first lens element L1with the convex surface facing the object side; a lens element L2 havingplane incident and exit surfaces and a reflecting surface; and abi-convex third lens element L3.

In the zoom lens system of Embodiment 3, the second lens unit G2, inorder from the object side to the image side, comprises: a bi-concavefourth lens element L4; and a positive meniscus fifth lens element L5with the convex surface facing the object side. Further, in the zoomlens system according to Embodiment 3, the third lens unit G3, in orderfrom the object side to the image side, comprises: a positive meniscussixth lens element L6 with the convex surface facing the object side; abi-convex seventh lens element L7; and a bi-concave eighth lens elementL8. Among these, the seventh lens element L7 and the eighth lens elementL8 are cemented with each other.

Furthermore, in the zoom lens system according to Embodiment 3, thefourth lens unit G4 comprises solely a positive meniscus ninth lenselement L9 with the convex surface facing the object side.

In the zoom lens system according to Embodiment 3, in zooming from thewide-angle limit to the telephoto limit, the second lens unit G2 movesto the image side while the third lens unit G3 moves to the object side.Further, the fourth lens unit G4 moves with locus of a convex to theobject side with changing the interval with the third lens unit G3. Thefirst lens unit G1 is fixed relative to the image surface S.

As shown in FIGS. 5A to 5C, in the zoom lens system according toEmbodiment 4, the first lens unit G1, in order from the object side tothe image side, comprises: a negative meniscus first lens element L1with the convex surface facing the object side; a lens element L2 havingplane incident and exit surfaces and a reflecting surface; and apositive meniscus third lens element L3 with the convex surface facingthe object side.

In the zoom lens system according to Embodiment 4, the second lens unitG2, in order from the object side to the image side, comprises: anegative meniscus fourth lens element L4 with the convex surface facingthe object side; a bi-concave fifth lens element L5; and a bi-convexsixth lens element L6.

Further, in the zoom lens system according to Embodiment 4, the thirdlens unit G3, in order from the object side to the image side,comprises: a positive meniscus seventh lens element L7 with the convexsurface facing the object side; a bi-convex eighth lens element L8; anda bi-concave ninth lens element L9. Among these, the eighth lens elementL8 and the ninth lens element L9 are cemented with each other.

Furthermore, in the zoom lens system according to Embodiment 4, thefourth lens unit G4 comprises solely a positive meniscus tenth lenselement L10 with the convex surface facing the object side.

In the zoom lens system according to Embodiment 4, in zooming from thewide-angle limit to the telephoto limit, the second lens unit G2 movesto the image side, while the third lens unit G3 and the fourth lens unitG4 move to the object side, and while the first lens unit G1 is fixedrelative to the image surface S.

As shown in FIGS. 8A to 8C, in the zoom lens system according toEmbodiment 5, the first lens unit G1, in order from the object side tothe image side, comprises: a negative meniscus first lens element L1with the convex surface facing the object side; a lens element L2 havingplane incident and exit surfaces and a reflecting surface; and abi-convex third lens element L3.

In the zoom lens system of Embodiment 5, the second lens unit G2, inorder from the object side to the image side, comprises: a negativemeniscus fourth lens element L4 with the convex surface facing theobject side; a bi-concave fifth lens element L5; and a positive meniscussixth lens element L6 with the convex surface facing the object side.

Further, in the zoom lens system of Embodiment 5, the third lens unitG3, in order from the object side to the image side, comprises: apositive meniscus seventh lens element L7 with the convex surface facingthe object side; a positive meniscus eighth lens element L8 with theconvex surface facing the object side; and a negative meniscus ninthlens element L9 with the convex surface facing the object side. Amongthese, the eighth lens element L8 and the ninth lens element L9 arecemented with each other.

Furthermore, in the zoom lens system according to Embodiment 5, thefourth lens unit G4 comprises solely a positive meniscus tenth lenselement L10 with the convex surface facing the object side.

In the zoom lens system according to Embodiment 5, in zooming from thewide-angle limit to the telephoto limit, the second lens unit G2 movesto the image side, while the third lens unit G3 and the fourth lens unitG4 move to the object side, and while the first lens unit G1 is fixedrelative to the image surface S.

As shown in FIGS. 11A to 11C, in the zoom lens system according toEmbodiment 6, the first lens unit G1, in order from the object side tothe image side, comprises: a negative meniscus first lens element L1with the convex surface facing the object side; a lens element L2 havingplane incident and exit surfaces and a reflecting surface; and abi-convex third lens element L3.

In the zoom lens system according to Embodiment 6, the second lens unitG2, in order from the object side to the image side, comprises: anegative meniscus fourth lens element L4 with the convex surface facingthe object side; a bi-concave fifth lens element L5; and a bi-convexsixth lens element L6.

Further, in the zoom lens system according to Embodiment 6, the thirdlens unit G3, in order from the object side to the image side,comprises: a bi-convex seventh lens element L7; a bi-convex eighth lenselement L8; and a bi-concave ninth lens element L9. Among these, theeighth lens element L8 and the ninth lens element L9 are cemented witheach other.

Furthermore, in the zoom lens system according to Embodiment 6, thefourth lens unit G4 comprises solely a positive meniscus tenth lenselement L10 with the convex surface facing the object side.

In the zoom lens system according to Embodiment 6, in zooming from thewide-angle limit to the telephoto limit, the second lens unit G2 and thefourth lens unit G4 move to the image side, while the third lens unit G3moves to the object side, and while the first lens unit G1 is fixedrelative to the image surface S.

As shown in FIGS. 14A to 14C, in the zoom lens system according toEmbodiment 7, the first lens unit G1, in order from the object side tothe image side, comprises: a bi-concave first lens element L1; a lenselement L2 having plane incident and exit surfaces and a reflectingsurface; and a bi-convex third lens element L3.

In the zoom lens system of Embodiment 7, the second lens unit G2, inorder from the object side to the image side, comprises: a positivemeniscus fourth lens element L4 with the convex surface facing theobject side; a positive meniscus fifth lens element L5 with the convexsurface facing the object side; and a negative meniscus sixth lenselement L6 with the convex surface facing the object side. Among these,the fifth lens element L5 and the sixth lens element L6 are cementedwith each other.

Further, in the zoom lens system of Embodiment 7, the third lens unit G3comprises solely a bi-convex seventh lens element L7.

In the zoom lens system according to Embodiment 7, in zooming from thewide-angle limit to the telephoto limit, the second lens unit G2 movesto the object side, while the third lens unit G3 moves to the imageside, and while the first lens unit G1 is fixed relative to the imagesurface S.

As described above, the zoom lens system according to Embodiments 3 to 7has a plurality of lens units each composed of at least one lenselement, while the first lens unit G1 includes a lens element having areflecting surface for bending the light beam from the object. However,the number of lens units constituting the zoom lens system is notlimited to a specific value. That is, a four-unit construction or athree-unit construction may be employed as in Embodiments 3 to 7, whileanother construction may be employed.

Further, preferably, a zoom lens system of four-unit constructioncomposed of four lens units, in order from the object side to the imageside, comprises: a first lens unit having positive optical power; asecond lens unit having negative optical power; and subsequent lensunits that include at least one lens unit having positive optical power.More preferably, for example, as in Embodiments 3 to 6, the subsequentlens units, in order from the object side to the image side, comprise athird lens unit having positive optical power and a fourth lens unithaving positive optical power.

Further, preferably, a zoom lens system of three-unit constructioncomposed of three lens units, in order from the object side to the imageside, comprises: a first lens unit having negative optical power; andsubsequent lens units that include at least one lens unit havingpositive optical power. More preferably, for example, as in Embodiment7, the subsequent lens units, in order from the object side to the imageside, comprise a second lens unit having positive optical power and athird lens unit having positive optical power.

Further, as in Embodiments 3 to 7, in the case of a zoom lens system offour-unit construction composed of four lens units or alternatively azoom lens system of three-unit construction composed of three lensunits, in zooming from the wide-angle limit to the telephoto limit atthe time of imaging, preferably, the first lens unit that includes thelens element having a reflecting surface does not move in the opticalaxis direction and is fixed relative to the image surface S.

In the zoom lens system according to Embodiments 3 to 7, an intervalbetween at least any two lens units among the plurality of lens units ischanged so that zooming is performed. Then, any one of these lens units,any one of the lens elements, or alternatively a plurality of adjacentlens elements that constitute one lens unit move in a directionperpendicular to the optical axis, so that blur caused in the image byhand blur, vibration or the like is compensated optically.

In each embodiment, the member that moves in a direction perpendicularto the optical axis is any one of the plurality of lens unitsconstituting the zoom lens system, any one of the lens elements thatconstitute a lens unit, or alternatively a plurality of adjacent lenselements that constitute one lens unit. As such, when any one of theselens units, any one of the lens elements, or alternatively a pluralityof adjacent lens elements that constitute one lens unit move in adirection perpendicular to the optical axis, image blur is compensatedin such a manner that size increase in the entire zoom lens system issuppressed while excellent imaging characteristics such as smalldecentering coma aberration and decentering astigmatism are satisfied.

In each embodiment, when a lens unit that does not include the lenselement having a reflecting surface, that is, any one of the lens unitsother than the first lens unit, any one of the lens elements other thanthe lens element having a reflecting surface, or alternatively aplurality of adjacent lens elements that are other than the lens elementhaving a reflecting surface and that constitute one lens unit move in adirection perpendicular to the optical axis, the entire zoom lens systemcan be constructed more compact. Further, image blur can be compensatedin a state that excellent imaging characteristics are satisfied. Thus,this construction is preferable. More preferably, any one of the lensunits other than the first lens unit moves in a direction perpendicularto the optical axis.

Further, in each embodiment, preferably, any one of the lens units oralternatively a plurality of adjacent lens elements constituting onelens unit, which move in a direction perpendicular to the optical axis,comprise three lens elements, from the perspective that image blur canbe compensated more satisfactorily in a state that excellent imagingcharacteristics are satisfied.

In the case of a zoom lens system of four-unit construction composed offour lens units as in Embodiments 3 to 6, preferably, the entirety ofthe third lens unit or alternatively part of the lens elements thatconstitute the third lens unit move in a direction perpendicular to theoptical axis. In the case of a zoom lens system of three-unitconstruction composed of three lens units as in Embodiment 7,preferably, the entirety of the second lens unit or alternatively partof the lens elements that constitute the second lens unit move in adirection perpendicular to the optical axis.

Conditions are described below that are preferably satisfied by a zoomlens system like the zoom lens system according to Embodiments 3 to 7having a plurality of lens units each composed of at least one lenselement, in which: an interval between at least any two lens units amongthe lens units is changed so that zooming is performed; a lens elementhaving a reflecting surface is included in a first lens unit among thelens units; and any one of the lens units, any one of the lens elements,or alternatively a plurality of adjacent lens elements that constituteone lens unit move in a direction perpendicular to the optical axis.Here, a plurality of preferable conditions are set forth for the zoomlens system according to each embodiment. The construction thatsatisfies all the plural conditions is most desirable for the zoom lenssystem. However, when an individual condition is satisfied, a zoom lenssystem providing the corresponding effect can be obtained.

For example, in a zoom lens system like the zoom lens system accordingto Embodiments 3 to 7, it is preferable that the following conditions(1) and (a) are satisfied;0.2<P _(W) /Y _(W)×10⁻³<1.7  (1)Z=f _(T) /f _(W)>2.5  (a)

where,

P_(w) is an optical axial distance between the reflecting surface and anobject side principal point of the lens unit or lens element that movesin a direction perpendicular to the optical axis, at the wide-anglelimit,

Y_(w) is an amount of movement at the time of maximum blur compensationfor the lens unit or lens element that moves in a directionperpendicular to the optical axis, in a focal length f_(w) of the entiresystem at the wide-angle limit,

f_(w) is a focal length of the entire zoom lens system at the wide-anglelimit, and

f_(T) is a focal length of the entire zoom lens system at the telephotolimit.

The condition (1) sets forth the optical axial distance from the lenselement having a reflecting surface to the lens unit or lens elementthat moves in a direction perpendicular to the optical axis. When thevalue exceeds the upper limit of the condition (1), the optical axialdistance from the lens element having a reflecting surface to the lensunit or lens element that moves in a direction perpendicular to theoptical axis increases, and so does the overall length of the zoom lenssystem. Thus, providing of a compact zoom lens system becomes difficult.In contrast, when the value goes below the lower limit of the condition(1), the amount of lens compensation increases so that excessivecompensation can be performed. This can cause large degradation in theoptical performance.

Here, when at least one of the following conditions (1)′ and (1)″ and(a) are satisfied, the above effect is achieved more successfully.0.2<P _(W) /Y _(W)×10⁻³<0.4  (1)′1.0<P _(W) /Y _(W)×10⁻³<1.7  (1)″Z=f _(T) /f _(W)>2.5  (a)

Further, for example, in a zoom lens system like the zoom lens systemaccording to Embodiments 3 to 7, it is preferable that the followingconditions (2) and (a) are satisfied;0.4<f ₁ /Y _(W)×10⁻³<1.5  (2)Z=f _(T) /f _(W)>2.5  (a)

where,

f₁ is a composite focal length of the first lens unit,

Y_(W) is the amount of movement at the time of maximum blur compensationfor the lens unit or lens element that moves in a directionperpendicular to the optical axis, in a focal length f_(W) of the entiresystem at the wide-angle limit,

f_(W) is the focal length of the entire zoom lens system at thewide-angle limit, and

f_(T) is the focal length of the entire zoom lens system at thetelephoto limit.

The condition (2) sets forth a condition concerning the aberrationperformance at the time of blur compensation. When the value exceeds theupper limit of the condition (2), aberration fluctuation becomes largein the entire zoom lens system. Thus, large coma aberration can occur,and hence this situation is undesirable. In contrast, when the valuegoes below the lower limit of the condition (2), the diameter increasesin the first lens unit that includes the lens element having areflecting surface. Thus, providing of a compact zoom lens systembecomes difficult.

Here, when at least one of the following conditions (2)′ and (2)″ and(a) are satisfied, the above effect is achieved more successfully.0.4<f ₁ /Y _(W)×10⁻³<0.6  (2)′1.0<f ₁ /Y _(W)×10⁻³<1.5  (2)″Z=f _(T) /f _(W)>2.5  (a)

Further, for example, in a zoom lens system like the zoom lens systemaccording to Embodiments 3 to 7, it is preferable that the followingconditions (3) and (a) are satisfied;0.1<PF/Y _(W)×10⁻³<1.0  (3)Z=f _(T) /f _(W)>2.5  (a)

where,

PF is an optical axial distance from a position on the most object sideon the optical axis of a lens element located on the most object side toa position on the most image side on the optical axis of the lenselement having a reflecting surface,

Y_(W) is the amount of movement at the time of maximum blur compensationfor the lens unit or lens element that moves in a directionperpendicular to the optical axis, in a focal length f_(W) of the entiresystem at the wide-angle limit,

f_(W) is the focal length of the entire zoom lens system at thewide-angle limit, and

f_(T) is the focal length of the entire zoom lens system at thetelephoto limit.

The condition (3) sets forth the thickness of the zoom lens system inthe longitudinal direction. When the value exceeds the upper limit ofthe condition (3), the thickness of the zoom lens system in thelongitudinal direction increases, so that providing of a compact imagingdevice or a compact camera becomes difficult. In contrast, when thevalue goes below the lower limit of the condition (3), ensuring of thesufficient distance set forth above for containing the lens elementhaving a reflecting surface becomes difficult.

Here, when at least one of the following conditions (3)′ and (3)″ and(a) are satisfied, the above effect is achieved more successfully.0.1<PF/Y _(W)×10⁻³<0.3  (3)′0.6<PF/Y _(W)×10⁻³<1.0  (3)″Z=f _(T) /f _(W)>2.5  (a)

Further, for example, in a zoom lens system like the zoom lens systemaccording to Embodiments 3 to 7, it is preferable that the followingcondition (4) is satisfied;1.0<H _(P) /H _(Y)<6.0  (4)

where,

H_(P) is an optical axial thickness of the lens element having areflecting surface, and

H_(Y) is an optical axial thickness of the lens unit or lens elementthat moves in a direction perpendicular to the optical axis.

The condition (4) sets forth the size of the lens element having areflecting surface. When the value exceeds the upper limit of thecondition (4), the lens element having a reflecting surface becomeslarge, so that providing of a compact zoom lens system becomesdifficult. In contrast, when the value goes below the lower limit of thecondition (4), the optical axial thickness of the lens unit or lenselement that moves in a direction perpendicular to the optical axisincreases, so that blur compensation becomes difficult.

Here, when at least one of the following conditions (4)′ and (4)″ issatisfied, the above effect is achieved more successfully.1.0<H _(P) /H _(Y)<3.0  (4)′4.5<H _(P) /H _(Y)<6.0  (4)″

Further, for example, in a zoom lens system like the zoom lens systemaccording to Embodiments 3 to 7, it is preferable that the followingcondition (5) is satisfied;0.3<M _(Y) /H _(P)<0.6  (5)

where,

M_(Y) is an amount of movement in the optical axis direction for thelens unit or lens element that moves in a direction perpendicular to theoptical axis in zooming from the wide-angle limit to the telephotolimit, and

H_(P) is the optical axial thickness of the lens element having areflecting surface.

The condition (5) sets forth the amount of movement in the optical axisdirection for the lens unit or lens element that moves in a directionperpendicular to the optical axis, relative to the optical axialthickness of the lens element having a reflecting surface. When thevalue exceeds the upper limit of the condition (5), the amount ofmovement in the optical axis direction for the lens unit or lens elementthat moves in a direction perpendicular to the optical axis increases,and so does the overall length of the zoom lens system. Thus, providingof a compact zoom lens system becomes difficult. In contrast, when thevalue goes below the lower limit of the condition (5), the optical axialthickness of the lens element having a reflecting surface increases.Thus, similarly, providing of a compact zoom lens system becomesdifficult.

Further, for example, in a zoom lens system like the zoom lens systemaccording to Embodiments 3 to 7, it is preferable that the followingconditions (6) and (a) are satisfied;0.1<M _(Y) /Y _(W)×10⁻³<0.4  (6)Z=f _(T) /f _(W)>2.5  (a)

where,

M_(Y) is the amount of movement in the optical axis direction for thelens unit or lens element that moves in a direction perpendicular to theoptical axis in zooming from the wide-angle limit to the telephotolimit,

Y_(W) is the amount of movement at the time of maximum blur compensationfor the lens unit or lens element that moves in a directionperpendicular to the optical axis, in a focal length f_(W) of the entiresystem at the wide-angle limit,

f_(W) is the focal length of the entire zoom lens system at thewide-angle limit, and

f_(T) is the focal length of the entire zoom lens system at thetelephoto limit.

The condition (6) sets forth the amount of movement in the optical axisdirection for the lens unit or lens element that moves in a directionperpendicular to the optical axis, relative to the amount of movement atthe time of maximum blur compensation for the lens unit or lens elementthat moves in a direction perpendicular to the optical axis. When thevalue exceeds the upper limit of the condition (6), the amount ofmovement in the optical axis direction for the lens unit or lens elementthat moves in a direction perpendicular to the optical axis increases,and so does the overall length of the zoom lens system. Thus, providingof a compact zoom lens system becomes difficult. In contrast, when thevalue goes below the lower limit of the condition (6), the amount oflens compensation increases so that excessive compensation can beperformed. This can cause degradation in the optical performance.

Further, for example, in a zoom lens system like the zoom lens systemaccording to Embodiments 3 to 7, it is preferable that the followingconditions (7) and (a) are satisfied;6.0<Y _(W) /I _(V)×10³<9.5  (7)Z=f _(T) /f _(W)>2.5  (a)

where,

Y_(W) is the amount of movement at the time of maximum blur compensationfor the lens unit or lens element that moves in a directionperpendicular to the optical axis, in a focal length f_(W) of the entiresystem at the wide-angle limit,

I_(V) is a length of the image sensor in the short side directionI _(V)=2×f _(W)×tan ω_(W)×0.60,

f_(W) is the focal length of the entire zoom lens system at thewide-angle limit,

ω_(W) is an incident half view angle at the wide-angle limit, and

f_(T) is the focal length of the entire zoom lens system at thetelephoto limit.

The condition (7) sets forth the amount of movement at the time ofmaximum blur compensation for the lens unit or lens element that movesin a direction perpendicular to the optical axis. When the value exceedsthe upper limit of the condition (7), the amount of lens compensationincreases so that excessive compensation can be performed. This cancause degradation in the optical performance. In contrast, when thevalue goes below the lower limit of the condition (7), sufficientcompensation of blur such as hand blur becomes difficult.

Further, for example, in a zoom lens system like the zoom lens systemaccording to Embodiments 3 to 7, it is preferable that the followingconditions (8) and (a) are satisfied;3.0<P _(W) /I _(V)<11.0  (8)Z=f _(T) /f _(W)>2.5  (a)

where,

P_(W) is the optical axial distance between the reflecting surface andan object side principal point of the lens unit or lens element thatmoves in a direction perpendicular to the optical axis, at thewide-angle limit,

I_(V) is the length of the image sensor in the short side directionI _(V)=2×f _(W)×tan ω_(W)×0.60,

f_(W) is the focal length of the entire zoom lens system at thewide-angle limit,

ω_(W) is the incident half view angle at the wide-angle limit, and

f_(T) is the focal length of the entire zoom lens system at thetelephoto limit.

The condition (8) sets forth the optical axial distance from the lenselement having a reflecting surface to the lens unit or lens elementthat moves in a direction perpendicular to the optical axis. When thevalue exceeds the upper limit of the condition (8), the optical axialdistance from the lens element having a reflecting surface to the lensunit or lens element that moves in a direction perpendicular to theoptical axis increases, and so does the overall length of the zoom lenssystem. Thus, providing of a compact zoom lens system becomes difficult.In contrast, when the value goes below the lower limit of the condition(8), satisfying of sufficient aberration performance becomes difficult.

Further, for example, in a zoom lens system like the zoom lens systemaccording to Embodiments 3 to 7, it is preferable that the followingconditions (9) and (a) are satisfied;0.2<f _(W) /H _(P)<0.9  (9)Z=f _(T) /f _(W)>2.5  (a)

where,

H_(P) is the optical axial thickness of the lens element having areflecting surface,

f_(W) is the focal length of the entire zoom lens system at thewide-angle limit, and

f_(T) is the focal length of the entire zoom lens system at thetelephoto limit.

The condition (9) sets forth the size of the lens element having areflecting surface. When the value exceeds the upper limit of thecondition (9), satisfying of sufficient aberration performance becomesdifficult. In contrast, when the value goes below the lower limit of thecondition (9), the lens element having a reflecting surface becomeslarge. Thus, providing of a compact zoom lens system becomes difficult.

Further, for example, in a zoom lens system like the zoom lens systemaccording to Embodiments 3 to 7, it is preferable that the followingconditions (10) and (a) are satisfied;2.5<H _(P) /I _(V)<5.0  (10)Z=f _(T) /f _(W)>2.5  (a)

where,

H_(P) is the optical axial thickness of the lens element having areflecting surface,

I_(V) is the length of the image sensor in the short side directionI _(V)=2×f _(W)×tan ω_(W)×0.60,

f_(W) is the focal length of the entire zoom lens system at thewide-angle limit,

ω_(W) is the incident half view angle at the wide-angle limit, and

f_(T) is the focal length of the entire zoom lens system at thetelephoto limit.

The condition (10) sets forth the thickness of the lens element having areflecting surface. When the value exceeds the upper limit of thecondition (10), the thickness increases in the lens element having areflecting surface. This causes a tendency of increase in the size ofthe imaging device. In contrast, when the value goes below the lowerlimit of the condition (10), ensuring of a sufficient thickness of thelens having a reflecting surface becomes difficult.

Here, when at least one of the following conditions (10)′ and (10)″ and(a) are satisfied, the above effect is achieved more successfully.2.5<H _(P) /I _(V)<3.0  (10)′4.0<H _(P) /I _(V)<5.0  (10)″Z=f _(T) /f _(W)>2.5  (a)

For example, in a zoom lens system composed of four lens units, in orderfrom the object side to the image side, comprising: a first lens unitincluding a lens element having a reflecting surface and having positiveoptical power; a second lens unit having negative optical power; a thirdlens unit having positive optical power; and a fourth lens unit havingpositive optical power, as in the zoom lens system according toEmbodiments 3 to 6, it is preferable that the following conditions (11)and (a) are satisfied;0.5<−(1−m _(2T))×m _(3T) ×m _(4T)<2.0  (11)Z=f _(T) /f _(W)>2.5  (a)

where,

m_(2T) is a magnification of the second lens unit at the telephoto limitin a case that the shooting distance is infinity,

m_(3T) is a magnification of the third lens unit at the telephoto limitin a case that the shooting distance is infinity,

m_(4T) is a magnification of the fourth lens unit at the telephoto limitin a case that the shooting distance is infinity,

f_(W) is the focal length of the entire zoom lens system at thewide-angle limit, and

f_(T) is the focal length of the entire zoom lens system at thetelephoto limit.

The condition (11) set forth a condition for obtaining satisfactoryimaging characteristics at the time of blur compensation. When the valueexceeds the upper limit of the condition (11), the amount of decenteringin the lens unit or lens element that moves in a direction perpendicularto the optical axis, which is necessary for realizing a predeterminedamount of decentering in the image, becomes excessively small. Thus,performing of accurate parallel translation becomes difficult. Incontrast, when the value goes below the lower limit of the condition(11), the amount of decentering in the lens unit or lens element thatmoves in a direction perpendicular to the optical axis, which isnecessary for realizing a predetermined amount of decentering in theimage, becomes excessively large. This causes a large change in theaberration, and hence causes a tendency of degradation in the imagingcharacteristics in the periphery of the image.

Here, when at least one of the following conditions (11)′ and (11)″ and(a) are satisfied, the above effect is achieved more successfully.1.0<−(1−m _(2T))×m _(3T) ×m _(4T)  (11)′−(1−m _(2T))×m _(3T) ×m _(4T)<1.5  (11)″Z=f _(T) /f _(W)>2.5  (a)

For example, in a zoom lens system composed of four lens units, in orderfrom the object side to the image side, comprising: a first lens unitincluding a lens element having a reflecting surface and having positiveoptical power; a second lens unit having negative optical power; a thirdlens unit having positive optical power; and a fourth lens unit havingpositive optical power, as in the zoom lens system according toEmbodiments 3 to 6, it is preferable that the following conditions (12)and (a) are satisfied;1.5<f ₁ /f ₃<3.5  (12)Z=f _(T) /f _(W)>2.5  (a)

where,

f₁ is the composite focal length of the first lens unit,

f₃ is a composite focal length of the third lens unit,

f_(W) is the focal length of the entire zoom lens system at thewide-angle limit, and

f_(T) is the focal length of the entire zoom lens system at thetelephoto limit.

The condition (12) sets forth the ratio between the composite focallength of the first lens unit and the composite focal length of thethird lens unit. When the value exceeds the upper limit of the condition(12), a tendency arises that a larger coma aberration is generated. Thissituation is undesirable. In contrast, when the value goes below thelower limit of the condition (12), the optical axial thickness of thefirst lens unit increases, so that providing of a compact zoom lenssystem becomes difficult.

Here, when at least one of the following conditions (12)′ and (12)″ and(a) are satisfied, the above effect is achieved more successfully.2.0<f ₁ /f ₃  (12)′f ₁ /f ₃<3.0  (12)″Z=f _(T) /f _(W)>2.5  (a)

For example, in a zoom lens system composed of four lens units, in orderfrom the object side to the image side, comprising: a first lens unitincluding a lens element having a reflecting surface and having positiveoptical power; a second lens unit having negative optical power; a thirdlens unit having positive optical power; and a fourth lens unit havingpositive optical power, as in the zoom lens system according toEmbodiments 3 to 6, it is preferable that the following conditions (13)and (a) are satisfied;1.0<−f ₁ /f ₂<4.0  (13)Z=f _(T) /f _(W)>2.5  (a)

where,

f₁ is the composite focal length of the first lens unit,

f₂ is a composite focal length of the second lens unit,

f_(W) is the focal length of the entire zoom lens system at thewide-angle limit, and

f_(T) is the focal length of the entire zoom lens system at thetelephoto limit.

The condition (13) sets forth the ratio between the composite focallength of the first lens unit and the composite focal length of thesecond lens unit. When the value exceeds the upper limit of thecondition (13), aberration fluctuation becomes large in the entire zoomlens system. This situation is undesirable. In contrast, when the valuegoes below the lower limit of the condition (13), the optical axialthickness of the first lens unit increases, so that providing of acompact zoom lens system becomes difficult.

Here, when at least one of the following conditions (13)′ and (13)″ and(a) are satisfied, the above effect is achieved more successfully.1.0<−f ₁ /f ₂<1.5  (13)′2.5<−f ₁ /f ₂<4.0  (13)″Z=f _(T) /f _(W)>2.5  (a)

For example, in a zoom lens system, in order from the object side to theimage side, comprising: a first lens unit having positive optical power;a second lens unit having negative optical power; a third lens unithaving positive optical power; and a fourth lens unit having positiveoptical power, as in the zoom lens system according to Embodiments 3 to6, it is preferable that the following conditions (14) and (a) aresatisfied;2.5<f ₄ /f _(W)<4.5  (14)Z=f _(T) /f _(W)>2.5  (a)

where,

f₄ is a composite focal length of the fourth lens unit,

f_(W) is the focal length of the entire zoom lens system at thewide-angle limit, and

f_(T) is the focal length of the entire zoom lens system at thetelephoto limit.

The condition (14) sets forth the focal length of the fourth lens unit.When the value exceeds the upper limit of the condition (14), it becomesdifficult that spherical aberration and surface curvature arecompensated with satisfactory balance in the entire zoom lens system. Incontrast, when the value goes below the lower limit of the condition(14), a tendency arises that the amount of movement at the time offocusing becomes large.

Here, when at least one of the following conditions (14)′ and (14)″ and(a) are satisfied, the above effect is achieved more successfully.3.0<f ₄ /f _(W)  (14)′f ₄ /f _(W)<3.5  (14)″Z=f _(T) /f _(W)>2.5  (a)

For example, in a zoom lens system, in order from the object side to theimage side, comprising: a first lens unit having positive optical power;a second lens unit having negative optical power; a third lens unithaving positive optical power; and a fourth lens unit having positiveoptical power, as in the zoom lens system according to Embodiments 3 to6, it is preferable that the following conditions (15) and (a) aresatisfied;0.9<β_(T4)/β_(W4)<1.2  (15)Z=f _(T) /f _(W)>2.5  (a)

where,

β_(T4) is a magnification of the fourth lens unit in the infinityin-focus condition at the telephoto limit,

β_(W4) is a magnification of the fourth lens unit in the infinityin-focus condition at the wide-angle limit,

f_(T) is the focal length of the entire zoom lens system at thetelephoto limit, and

f_(W) is the focal length of the entire zoom lens system at thewide-angle limit.

The condition (15) sets forth the magnification variation in the fourthlens unit, and hence sets forth zoom contribution of the fourth lensunit. When the value exceeds the upper limit of the condition (15), itbecomes difficult that aberration is compensated in the entire zoom lenssystem with satisfactory balance. In contrast, when the value goes belowthe lower limit of the condition (15), a desired zoom ratio becomesdifficult to be obtained.

Here, when the following conditions (15)′ and (a) are satisfied, theabove effect is achieved more successfully.1.0<β_(T4)/β_(W4)  (15)′Z=f _(T) /f _(W)>2.5  (a)

For example, in a zoom lens system, in order from the object side to theimage side, comprising: a first lens unit having positive optical power;a second lens unit having negative optical power; a third lens unithaving positive optical power; and a fourth lens unit having positiveoptical power, as in the zoom lens system according to Embodiments 3 to6, it is preferable that the following conditions (16) and (a) aresatisfied;0.5<f ₃ /f ₄<1.2  (16)Z=f _(T) /f _(W)>2.5  (a)

where,

f₃ is the composite focal length of the third lens unit,

f₄ is the composite focal length of the fourth lens unit,

f_(W) is the focal length of the entire zoom lens system at thewide-angle limit, and

f_(T) is the focal length of the entire zoom lens system at thetelephoto limit.

The condition (16) sets forth the ratio of the focal lengths of thethird lens unit and the fourth lens unit, and hence sets forth thefunction of each lens unit in zooming. When the value exceeds the upperlimit of the condition (16), zooming effect decreases in the third lensunit. Thus, a desired zoom ratio becomes difficult to be obtained. Incontrast, when the value goes below the lower limit of the condition(16), it becomes difficult that astigmatism is compensated in the entirezoom lens system.

Here, when at least one of the following conditions (16)′ and (16)″ and(a) are satisfied, the above effect is achieved more successfully.0.5<f ₃ /f ₄<0.8  (16)′1.0<f ₃ /f ₄<1.2  (16)″Z=f _(T) /f _(W)>2.5  (a)

The zoom lens system according to Embodiments 3 to 6 is a zoom lenssystem having a four-unit construction of positive, negative, positiveand positive, and in order from the object side to the image side,comprising: a first lens unit G1 having positive optical power; a secondlens unit G2 having negative optical power; a diaphragm A; a third lensunit G3 having positive optical power; and a fourth lens unit G4 havingpositive optical power. Further, the zoom lens system according toEmbodiment 7 is a zoom lens system having a three-unit construction ofnegative, positive and positive, and in order from the object side tothe image side, comprising: a first lens unit G1 having negative opticalpower; a diaphragm A; a second lens unit G2 having positive opticalpower; and a third lens unit G3 having positive optical power. However,the present invention is not limited to these constructions. That is,various constructions are employable like a three-unit construction ofnegative, positive and negative, a three-unit construction of positive,negative and positive, a four-unit construction of positive, negative,positive and negative, and a five-unit construction of positive,negative, positive, negative and positive. Such zoom lens systems cansuitably be employed in the imaging device, for example, shown inEmbodiments 1 and 2.

Here, the lens units constituting the zoom lens system of Embodiments 3to 7 are composed exclusively of refractive type lens elements thatdeflect the incident light by refraction (that is, lens elements of atype in which deflection is achieved at the interface between media eachhaving a distinct refractive index). However, the present invention isnot limited to the zoom lens system of this construction. For example,the lens units may employ diffractive type lens elements that deflectthe incident light by diffraction; refractive-diffractive hybrid typelens elements that deflect the incident light by a combination ofdiffraction and refraction; or gradient index type lens elements thatdeflect the incident light by distribution of refractive index in themedium.

An imaging device comprising a zoom lens system according to Embodiments3 to 7 described above and an image sensor such as a CCD or a CMOS maybe applied to a mobile telephone, a PDA (Personal Digital Assistance), asurveillance camera in a surveillance system, a Web camera, avehicle-mounted camera or the like.

Further, the construction of the digital still camera and the zoom lenssystem according to Embodiments 3 to 7 described above is applicablealso to a digital video camera for moving images. In this case, movingimages with high resolution can be acquired in addition to still images.

Hereinafter, numerical examples which are actual implementations of thezoom lens systems according to Embodiments 3 to 7 will be described. Inthe numerical examples, the units of the length in the tables are all“mm”. Moreover, in the numerical examples, r is the radius of curvature,d is the axial distance, nd is the refractive index to the d-line, andνd is the Abbe number to the d-line. In the numerical examples, thesurfaces marked with * are aspherical surfaces, and the asphericalsurface configuration is defined by the following expression.

$Z = {\frac{h^{2}/r}{1 + \sqrt{1 - {\left( {1 + \kappa} \right)\left( {h/r} \right)^{2}}}} + {Dh}^{4} + {Eh}^{6} + {Fh}^{8} + {Gh}^{10}}$Here, κ is the conic constant, D, E, F and G are a fourth-order,sixth-order, eighth-order and tenth-order aspherical coefficients,respectively.

FIGS. 3A to 3I are longitudinal aberration diagrams of a zoom lenssystem according to Example 1. FIGS. 6A to 6I are longitudinalaberration diagrams of a zoom lens system according to Example 2. FIGS.9A to 9I are longitudinal aberration diagrams of a zoom lens systemaccording to Example 3. FIGS. 12A to 12I are longitudinal aberrationdiagrams of a zoom lens system according to Example 4. FIGS. 15A to 15Iare longitudinal aberration diagrams of a zoom lens system according toExample 5.

FIGS. 3A to 3C, 6A to 6C, 9A to 9C, 12A to 12C, and 15A to 15C show thelongitudinal aberration at the wide-angle limit. FIGS. 3D to 3F, 6D to6F, 9D to 9F, 12D to 12F, and 15D to 15F show the longitudinalaberration at the middle position. FIGS. 3G to 3I, 6G to 6I, 9G to 9I,12G to 12I, and 15G to 15I show the longitudinal aberration at thetelephoto limit. FIGS. 3A, 3D, 3G, 6A, 6D, 6G, 9A, 9D, 9G, 12A, 12D,12G, 15A, 15D and 15G are spherical aberration diagrams. FIGS. 3B, 3E,3H, 6B, 6E, 6H, 9B, 9E, 9H, 12B, 12E, 12H, 15B, 15E and 15H areastigmatism diagrams. FIGS. 3C, 3F, 3I, 6C, 6F, 6I, 9C, 9F, 9I, 12C,12F, 12I, 15C, 15F and 15I are distortion diagrams. In each sphericalaberration diagram, the vertical axis indicates the F-number, and thesolid line, the short dash line and the long dash line indicate thecharacteristics to the d-line, the F-line and the C-line, respectively.In each astigmatism diagram, the vertical axis indicates the half viewangle, and the solid line and the dash line indicate the characteristicsto the sagittal image plane (in each FIG., indicated as “s”) and themeridional image plane (in each FIG., indicated as “m”), respectively.In each distortion diagram, the vertical axis indicates the half viewangle.

FIGS. 4A to 4F are lateral aberration diagrams of a zoom lens systemaccording to Example 1 at the telephoto limit. FIGS. 7A to 7F arelateral aberration diagrams of a zoom lens system according to Example 2at the telephoto limit. FIGS. 10A to 10F are lateral aberration diagramsof a zoom lens system according to Example 3 at the telephoto limit.FIGS. 13A to 13F are lateral aberration diagrams of a zoom lens systemaccording to Example 4 at the telephoto limit. FIGS. 16A to 16F arelateral aberration diagrams of a zoom lens system according to Example 5at the telephoto limit.

FIGS. 4A to 4C, 7A to 7C, 10A to 10C, 13A to 13C, and 16A to 16C arelateral aberration diagrams at the telephoto limit corresponding to abasic state that image blur compensation is not performed. FIGS. 4D to4F, 7D to 7F, 10D to 10F, and 13D to 13F are lateral aberration diagramscorresponding to an image blur compensation state at the telephoto limitin which the entirety of the third lens unit G3 is moved by apredetermined amount in a direction perpendicular to the optical axis.FIGS. 16D to 16F are lateral aberration diagrams corresponding to animage blur compensation state at the telephoto limit in which theentirety of the second lens unit G2 is moved by a predetermined amountin a direction perpendicular to the optical axis. Among the lateralaberration diagrams corresponding to the basic state, FIGS. 4A, 7A, 10A,13A and 16A show the lateral aberration at an image point at 75% of themaximum image height. FIGS. 4B, 7B, 10B, 13B and 16B show the lateralaberration at the axial image point. FIGS. 4C, 7C, 10C, 13C and 16C showthe lateral aberration at an image point at −75% of the maximum imageheight. Among the lateral aberration diagrams corresponding to the imageblur compensation state, FIGS. 4D, 7D, 10D, 13D and 16D show the lateralaberration at an image point at 75% of the maximum image height. FIGS.4E, 7E, 10E, 13E and 16E show the lateral aberration at the axial imagepoint. FIGS. 4F, 7F, 10F, 13F and 16F show the lateral aberration at animage point at −75% of the maximum image height. In each lateralaberration diagram, the horizontal axis indicates the distance from theprincipal ray on the pupil surface, and the solid line, the short dashline and the long dash line indicate the characteristics to the d-line,the F-line and the C-line, respectively. In the lateral aberrationdiagrams of FIGS. 4A to 4F, 7A to 7F, 10A to 10F, and 13A to 13F, themeridional image plane is adopted as the plane containing the opticalaxis of the first lens unit G1 and the optical axis of the third lensunit G3. In the lateral aberration diagram of FIGS. 16A to 16F, themeridional image plane is adopted as the plane containing the opticalaxis of the first lens unit G1 and the optical axis of the second lensunit G2.

Here, the amount of movement in a direction perpendicular to the opticalaxis of the third lens unit G3 in the image blur compensation state is0.096 mm in Example 1, 0.094 mm in Example 2, 0.140 mm in Example 3, and0.100 mm in Example 4. The amount of movement in a directionperpendicular to the optical axis of the second lens unit G2 in theimage blur compensation state in Example 5 is 0.059 mm. Here, the amountof image decentering in a case that the zoom lens system inclines by0.3° when the shooting distance is infinity at the telephoto limit isequal to the amount of image decentering in a case that the entirety ofthe third lens unit G3 or the entirety of the second lens unit G2 movesin parallel in a direction perpendicular to the optical axis by each ofthe above values.

As seen from the lateral aberration diagrams, satisfactory symmetry isobtained in the lateral aberration at the axial image point. Further,when the lateral aberration at the +75% image point and the lateralaberration at the −75% image point are compared with each other in thebasic state, all have a small degree of curvature and almost the sameinclination in the aberration curve. Thus, decentering coma aberrationand decentering astigmatism are small. This indicates that sufficientimaging performance is obtained even in the image blur compensationstate. Further, when the image blur compensation angle of a zoom lenssystem is the same, the amount of parallel movement required for imageblur compensation decreases with decreasing focal length of the entirezoom lens system. Thus, at arbitrary zoom positions, sufficient imageblur compensation can be performed for image blur compensation angles upto 0.3° without degrading the imaging characteristics.

EXAMPLE 1

A zoom lens system of Example 1 corresponds to that of Embodiment 3shown in FIGS. 2A to 2C. Table 1 shows the lens data of the zoom lenssystem of Example 1. Table 2 shows the focal length, the F-number, thehalf view angle, the optical overall length and the variable axialdistance data, when the shooting distance is infinity. Table 3 shows theaspherical data.

TABLE 1 Lens Sur- Lens unit element face r d nd νd G1 L1 1 26.433 1.0001.84666 23.8 2 13.068 4.195 L2 3 ∞ 12.000 1.84666 23.8 4 ∞ 0.300 L3 530.525 3.323 1.72916 54.7 6 −28.970 Variable G2 L4 7 −17.932 * 0.8001.66547 55.2 8 7.149 * 0.792 L5 9 8.668 2.300 1.84666 23.8 10 17.616Variable Diaphragm 11 ∞ 1.900 G3 L6 12 7.079 1.800 1.72916 54.7 13770.451 1.619 L7 14 9.327 * 1.900 1.66547 55.2 L8 15 −28.836 0.7001.84666 23.8 16 5.490 Variable G4 L9 17 8.399 * 2.150 1.80470 41.0 1818.335 Variable P 19 ∞ 2.100 1.51680 64.2 20 ∞ —

TABLE 2 Axial Wide-angle Middle Telephoto distance limit position limitd6 0.700 10.040 15.843 d10 20.000 9.212 0.300 d16 7.142 7.290 10.899 d180.998 2.299 1.790 f 5.81 11.61 23.19 F 2.86 3.01 3.50 ω 33.58 16.83 8.62

TABLE 3 Sur- face κ D E F G 7 0.00E+00  2.35E−04 −1.65E−06 −2.82E−083.95E−10 8 0.00E+00  9.38E−05 −1.74E−06  9.24E−09 −4.00E−09  14 0.00E+00−7.14E−04  8.27E−07 −6.21E−06 4.36E−07 17 0.00E+00 −3.47E−05  1.77E−06 2.34E−08 2.22E−10

EXAMPLE 2

A zoom lens system of Example 2 corresponds to that of Embodiment 4shown in FIGS. 5A to 5C. Table 4 shows the lens data of the zoom lenssystem of Example 2. Table 5 shows the focal length, the F-number, thehalf view angle, the optical overall length and the variable axialdistance data, when the shooting distance is infinity. Table 6 shows theaspherical data.

TABLE 4 Lens Sur- Lens unit element face r d nd νd G1 L1 1 31.796 1.0001.84666 23.8 2 22.088 6.895 L2 3 ∞ 19.000 1.84666 23.8 4 ∞ 0.300 L3 523.158 3.891 1.72916 54.7 6 286.387 Variable G2 L4 7 21.533 1.0001.80610 33.3 8 8.481 4.626 L5 9 −24.301 * 0.800 1.66547 55.2 10 14.139 *0.792 L6 11 16.605 2.300 1.84666 23.8 12 −188.578 Variable Diaphragm 13∞ 1.900 G3 L7 14 8.227 1.800 1.72916 54.7 15 596.126 1.619 L8 16 8.336 *1.900 1.66547 55.2 L9 17 −89.535 0.700 1.84666 23.8 18 5.717 Variable G4L10 19 10.386 * 2.150 1.80470 41.0 20 20.893 Variable P 21 ∞ 2.1001.51680 64.2 22 ∞ —

TABLE 5 Axial Wide-angle Middle Telephoto distance limit position limitd6 0.800 10.802 16.304 d12 23.001 10.791 0.300 d18 4.470 6.016 10.702d20 3.139 3.795 4.109 f 5.83 11.60 23.19 F 2.82 3.14 3.84 ω 32.89 17.388.77

TABLE 6 Sur- face κ D E F G 9 0.00E+00 −2.36E−04 9.10E−06 −1.16E−073.13E−10 10 0.00E+00 −2.45E−04 9.51E−06 −1.11E−07 1.95E−11 16 0.00E+00−3.68E−04 −7.08E−06  −8.59E−07 3.71E−08 19 0.00E+00 −7.40E−05 1.70E−06−6.65E−08 1.54E−09

EXAMPLE 3

A zoom lens system of Example 3 corresponds to that of Embodiment 5shown in FIGS. 8A to 8C. Table 7 shows the lens data of the zoom lenssystem of Example 3. Table 8 shows the focal length, the F-number, thehalf view angle, the optical overall length and the variable axialdistance data, when the shooting distance is infinity. Table 9 shows theaspherical data.

TABLE 7 Lens Sur- Lens unit element face r d nd νd G1 L1 1 31.342 1.0001.84666 23.8 2 24.108 9.041 L2 3 ∞ 21.999 1.84666 23.8 4 ∞ 0.300 L3 526.664 3.694 1.72916 54.7 6 −3977.414 Variable G2 L4 7 20.695 1.0001.80610 33.3 8 8.587 4.296 L5 9 −32.379 * 0.800 1.66547 55.2 10 15.056 *0.792 L6 11 14.436 2.300 1.84666 23.8 12 80.361 Variable Diaphragm 13 ∞0.900 G3 L7 14 7.837 1.800 1.72916 54.7 15 78.733 1.619 L8 16 9.314 *1.900 1.66547 55.2 L9 17 3273.257 0.700 1.84666 23.8 18 5.670 VariableG4 L10 19 8.483 * 2.150 1.80470 41.0 20 18.884 Variable P 21 ∞ 2.1001.51680 64.2 22 ∞ —

TABLE 8 Axial Wide-angle Middle Telephoto distance limit position limitd6 0.800 9.981 17.251 d12 28.037 15.627 0.687 d18 3.211 6.211 13.852 d204.200 4.422 4.458 f 5.83 11.59 28.99 F 2.84 3.24 4.16 ω 33.05 17.58 7.30

TABLE 9 Sur- face κ D E F G 9 0.00E+00 −2.55E−04 9.37E−06 −1.24E−075.37E−10 10 0.00E+00 −2.12E−04 9.18E−06 −8.61E−08 −9.73E−12  16 0.00E+00−3.65E−04 −1.10E−05  −1.72E−07 4.51E−09 19 0.00E+00 −5.61E−05 2.15E−06−7.85E−08 1.23E−09

EXAMPLE 4

A zoom lens system of Example 4 corresponds to that of Embodiment 6shown in FIGS. 11A to 11C. Table 10 shows the lens data of the zoom lenssystem of Example 4. Table 11 shows the focal length, the F-number, thehalf view angle, the optical overall length and the variable axialdistance data, when the shooting distance is infinity. Table 12 showsthe aspherical data.

TABLE 10 Lens Sur- Lens unit element face r d nd νd G1 L1 1 26.145 11.84666 23.8 2 19.462 9.241 L2 3 ∞ 20 1.84666 23.8 4 ∞ 0.3 L3 5 26.4454.025 1.72000 50.3 6 −195.628 Variable G2 L4 7 44.928 1 1.80610 33.3 88.149 4.685 L5 9 −30.882 * 0.8 1.66547 55.2 10 31.268 * 0.792 L6 1122.734 2.3 1.84666 23.8 12 −62.669 Variable Diaphragm 13 ∞ 0.9 G3 L7 1417.19 4.003 1.72916 54.7 15 −51.573 1.619 L8 16 7.269 * 2.498 1.6654755.2 L9 17 −1747.278 0.7 1.84666 23.8 18 5.832 Variable G4 L10 197.982 * 2.15 1.80470 41.0 20 15.306 Variable P 21 ∞ 2.100 1.51680 64.222 ∞ —

TABLE 11 Axial Wide-angle Middle Telephoto distance limit position limitd6 0.800 9.959 17.001 d12 26.002 12.580 0.455 d18 0.799 5.097 11.028 d205.991 5.952 5.115 f 5.84 11.60 23.19 F 2.87 3.29 3.83 ω 33.45 18.01 9.17

TABLE 12 Sur- face κ D E F G 9 0.00E+00 −2.54E−04 1.08E−05 −7.97E−08−3.59E−10 10 0.00E+00 −2.47E−04 1.11E−05 −1.05E−07 −2.62E−10 16 0.00E+00 2.56E−05 −1.53E−05   2.75E−06 −1.65E−07 19 0.00E+00 −9.85E−05 1.04E−06−5.24E−08  5.15E−10

EXAMPLE 5

A zoom lens system of Example 5 corresponds to that of Embodiment 7shown in FIGS. 14A to 14C. Table 13 shows the lens data of the zoom lenssystem of Example 5. Table 14 shows the focal length, the F-number, thehalf view angle, the optical overall length and the variable axialdistance data, when the shooting distance is infinity. Table 15 showsthe aspherical data.

TABLE 13 Lens Sur- Lens unit element face r d nd νd G1 L1 1 −21.2990.800 1.80470 41.0 2 10.906 * 0.969 L2 3 ∞ 8.000 1.84666 23.8 4 ∞ 0.000L3 5 38.692 1.400 1.84666 23.8 6 −44.535 Variable Diaphragm 7 ∞ 0.900 G2L4 8 4.830 * 1.350 1.80470 41.0 9 73.288 0.300 L5 10 9.794 0.900 1.6968055.5 L6 11 53.632 0.400 1.80518 25.5 12 3.392 Variable G3 L7 13 13.347 *1.810 1.60602 57.4 14 −16.862 * Variable P 15 ∞ 0.900 1.51680 64.2 16 ∞—

TABLE 14 Axial Wide-angle Middle Telephoto distance limit position limitd6 14.008 8.080 0.821 d12 3.688 11.120 19.641 d14 4.151 2.639 1.380 f6.420 10.050 17.090 F 3.33 4.60 6.55 ω 30.89 19.77 11.77

TABLE 15 Sur- face κ D E F G 2  2.20E+00 −5.38E−04  −4.61E−06 7.64E−08−6.47E−09 8 −5.60E−01 6.59E−06  1.14E−05 −2.31E−06   1.75E−07 13−1.59E+01 1.39E−03 −8.03E−05 2.89E−06 −6.19E−08 14  2.65E+00 1.13E−03−7.44E−05 2.55E−06 −5.01E−08

The corresponding values to the above conditions are listed in thefollowing Table 16.

TABLE 16 Example Condition 1 2 3 4 5 (1) P_(W)/Y_(W) × 10⁻³ 1.08 1.401.20 1.30 0.34 (2) f₁/Y_(W) × 10⁻³ 1.06 1.39 1.07 1.12 0.52 (3) PF/Y_(W)× 10⁻³ 0.61 0.87 0.82 0.89 0.23 (4) H_(P)/H_(Y) 1.99 3.16 3.66 5.00 2.71(5) M_(Y)/H_(P) 0.38 0.38 0.50 0.47 1.65 (6) M_(Y)/Y_(W) × 10⁻³ 0.160.23 0.28 0.27 0.31 (7) Y_(W)/I_(V) × 10³ 6.05 6.85 8.57 7.34 9.11 (8)P_(W)/I_(V) 6.54 9.60 10.29 9.57 3.14 (9) f_(W)/H_(P) 0.48 0.31 0.270.29 0.80 (10) H_(P)/I_(V) 2.59 4.20 4.83 4.32 — (11) −(1 − m_(2T)) ×m_(3T) × m_(4T) 1.41 1.20 1.29 1.02 — (12) f₁/f₃ 2.21 2.91 2.37 1.78 —(13) −f₁/f₂ 2.31 3.10 2.86 2.30 — (14) f₄/f_(W) 3.02 4.04 3.01 3.14 —(15) β_(T4)/β_(W4) 0.93 0.94 0.97 1.11 — (16) f₃/f₄ 0.77 0.63 1.01 1.16—

The zoom lens system according to the present invention is applicable toa digital input device such as a digital still camera, a digital videocamera, a mobile telephone, a PDA (Personal Digital Assistance), asurveillance camera in a surveillance system, a Web camera or avehicle-mounted camera. In particular, the present zoom lens system issuitable for a camera such as a digital still camera or a digital videocamera requiring high image quality.

Although the present invention has been fully described by way ofexample with reference to the accompanying drawings, it is to beunderstood that various changes and modifications will be apparent tothose skilled in the art. Therefore, unless otherwise such changes andmodifications depart from the scope of the present invention, theyshould be construed as being included therein.

1. A zoom lens system comprising: a plurality of lens units eachcomposed of at least one lens element, wherein an interval between atleast any two lens units among the lens units is changed so that anoptical image of an object is formed with a continuously variablemagnification, a first lens unit arranged on the most object side amongthe lens units includes a lens element having a reflecting surface forbending a light beam from the object, and has negative optical power,and any one of the lens units, any one of the lens elements, oralternatively a plurality of adjacent lens elements that constitute onelens unit move in a direction perpendicular to an optical axis.
 2. Thezoom lens system as claimed in claim 1, wherein any one of the lensunits other than the first lens unit, any one of the lens elements otherthan the lens element having a reflecting surface, or alternatively aplurality of adjacent lens elements that are other than the lens elementhaving a reflecting surface and that constitute one lens unit move in adirection perpendicular to the optical axis.
 3. The zoom lens system asclaimed in claim 1, wherein any one of the lens units or alternatively aplurality of adjacent lens elements constituting one lens unit, whichmove in a direction perpendicular to the optical axis, are composed ofthree lens elements.
 4. The zoom lens system as claimed in claim 1,wherein the reflecting surface bends by approximately 90° an axialprincipal ray from the object.
 5. The zoom lens system as claimed inclaim 1, wherein the lens element having a reflecting surface is aprism.
 6. The zoom lens system as claimed in claim 5, wherein the prismhas optical power.
 7. The zoom lens system as claimed in claim 1,wherein the lens element having a reflecting surface is a mirror.
 8. Thezoom lens system as claimed in claim 1, wherein the first lens unit, inorder from the object side to the image side, comprises: a lens elementhaving negative optical power; a lens element having a reflectingsurface; and subsequent lens elements including at least one lenselement and having positive optical power.
 9. The zoom lens system asclaimed in claim 1, satisfying the following conditions (1) and (a):0.2<P _(W) /Y _(W)×10⁻³<1.7  (1)Z=f _(T) /f _(W)>2.5  (a) wherein, P_(W) is an optical axial distancebetween the reflecting surface and an object side principal point of thelens unit or lens element that moves in a direction perpendicular to theoptical axis, at the wide-angle limit, Y_(W) is an amount of movement atthe time of maximum blur compensation for the lens unit or lens elementthat moves in a direction perpendicular to the optical axis, in a focallength f_(W) of the entire system at the wide-angle limit, f_(W) is afocal length of the entire zoom lens system at a wide-angle limit, andf_(T) is a focal length of the entire zoom lens system at a telephotolimit.
 10. The zoom lens system as claimed in claim 1, satisfying thefollowing conditions (2) and (a):0.4<f ₁ /Y _(w)×10⁻³<1.5  (2)Z=f _(T) /f _(W)>2.5  (a) wherein, f₁ is a composite focal length of thefirst lens unit, Y_(W) is the amount of movement at the time of maximumblur compensation for the lens unit or lens element that moves in adirection perpendicular to the optical axis, in a focal length f_(W) ofthe entire system at the wide-angle limit, f_(W) is the focal length ofthe entire zoom lens system at a wide-angle limit, and f_(T) is thefocal length of the entire zoom lens system at a telephoto limit. 11.The zoom lens system as claimed in claim 1, satisfying the followingconditions (3) and (a):0.1<PF/Y _(W)×10⁻³<1.0  (3)Z=f _(T) /f _(W)>2.5  (a) wherein, PF is an optical axial distance froma position on the most object side on the optical axis of a lens elementlocated on the most object side to a position on the most image side onthe optical axis of the lens element having a reflecting surface, Y_(W)is the amount of movement at the time of maximum blur compensation forthe lens unit or lens element that moves in a direction perpendicular tothe optical axis, in a focal length f_(W) of the entire system at thewide-angle limit, f_(W) is the focal length of the entire zoom lenssystem at a wide-angle limit, and f_(T) is the focal length of theentire zoom lens system at a telephoto limit.
 12. The zoom lens systemas claimed in claim 1, satisfying the following condition (4):1.0<H _(P) /H _(Y)<6.0  (4) wherein, H_(P) is an optical axial thicknessof the lens element having a reflecting surface, and H_(Y) is an opticalaxial thickness of the lens unit or lens element that moves in adirection perpendicular to the optical axis.
 13. The zoom lens system asclaimed in claim 1, satisfying the following condition (5):0.3<M _(Y) H _(P)<0.6  (5) wherein, M_(Y) is an amount of movement inthe optical axis direction for the lens unit or lens element that movesin a direction perpendicular to the optical axis in zooming from thewide-angle limit to the telephoto limit, and H_(P) is the optical axialthickness of the lens element having a reflecting surface.
 14. The zoomlens system as claimed in claim 1, satisfying the following conditions(6) and (a):0.1<M _(Y) /Y _(W)×10⁻³<0.4  (6)Z=f _(T) /f _(W)>2.5  (a) wherein, M_(Y) is the amount of movement inthe optical axis direction for the lens unit or lens element that movesin a direction perpendicular to the optical axis in zooming from thewide-angle limit to the telephoto limit, Y_(W) is the amount of movementat the time of maximum blur compensation for the lens unit or lenselement that moves in a direction perpendicular to the optical axis, ina focal length f_(W) of the entire system at the wide-angle limit, f_(W)is the focal length of the entire zoom lens system at a wide-anglelimit, and f_(T) is the focal length of the entire zoom lens system at atelephoto limit.
 15. The zoom lens system as claimed in claim 1,satisfying the following conditions (7) and (a):6.0<Y _(W) /I _(V)×10³<9.5  (7)Z=f _(T) /f _(W)>2.5  (a) wherein, Y_(W) is the amount of movement atthe time of maximum blur compensation for the lens unit or lens elementthat moves in a direction perpendicular to the optical axis, in a focallength f_(W) of the entire system at the wide-angle limit, I_(V) is alength of the image sensor in the short side directionI_(V)=2×f_(W)×tanω_(W)×0.60, f_(W) is the focal length of the entirezoom lens system at a wide-angle limit, ω_(W) is an incident half viewangle at the wide-angle limit, and f_(T) is the focal length of theentire zoom lens system at a telephoto limit.
 16. The zoom lens systemas claimed in claim 1, satisfying the following conditions (8) and (a):3.0<P _(W) /I _(V)<11.0  (8)Z=f _(T) /f _(W)>2.5  (a) wherein, P_(W) is the optical axial distancebetween the reflecting surface and an object side principal point of thelens unit or lens element that moves in a direction perpendicular to theoptical axis, at the wide-angle limit, I_(V) is the length of the imagesensor in the short side direction I_(V)=2×f_(W)×tanω_(W)×0.60, f_(W) isthe focal length of the entire zoom lens system at a wide-angle limit,107 _(W) is the incident half view angle at the wide-angle limit, andf_(T) is the focal length of the entire zoom lens system at a telephotolimit.
 17. The zoom lens system as claimed in claim 1, satisfying thefollowing conditions (9) and (a):0.2<f _(W) /H _(P)<0.9  (9)Z=f _(T) /f _(W)>2.5  (a) wherein, H_(P) is the optical axial thicknessof the lens element having a reflecting surface, f_(W) is the focallength of the entire zoom lens system at a wide-angle limit, and f_(T)is the focal length of the entire zoom lens system at a telephoto limit.18. The zoom lens system as claimed in claim 1, comprising three lensunits.
 19. The zoom lens system as claimed in claim 18, wherein inzooming from the wide-angle limit to the telephoto limit at the time ofimaging, the first lens unit does not move in the optical axisdirection.
 20. The zoom lens system as claimed in claim 18, wherein theentirety of the second lens unit moves in a direction perpendicular tothe optical axis.
 21. The zoom lens system as claimed in claim 18,wherein part of lens elements that constitute the second lens unit movein a direction perpendicular to the optical axis.
 22. The zoom lenssystem as claimed in claim 18, comprising: a first lens unit havingnegative optical power; and subsequent lens units that include at leastone lens unit having positive optical power.
 23. The zoom lens system asclaimed in claim 22, wherein the subsequent lens units, in order fromthe object side to the image side, comprise a second lens unit havingpositive optical power and a third lens unit having positive opticalpower.
 24. An imaging device capable of outputting an optical image ofan object as an electric image signal, comprising: a zoom lens systemthat forms the optical image of the object; and an image sensor thatconverts the optical image formed by the zoom lens system into theelectric image signal, wherein the zoom lens system comprises aplurality of lens units each composed of at least one lens element, inwhich an interval between at least any two lens units among the lensunits is changed so that an optical image of an object is formed with acontinuously variable magnification, a first lens unit arranged on themost object side among the lens units includes a lens element having areflecting surface for bending a light beam from the object, and hasnegative optical power, and any one of the lens units, any one of thelens elements, or alternatively a plurality of adjacent lens elementsthat constitute one lens unit move in a direction perpendicular to anoptical axis.
 25. A camera for converting an optical image of an objectinto an electric image signal and then performing at least one ofdisplaying and storing of the converted image signal, comprising: animaging device including a zoom lens system that forms the optical imageof the object and an image sensor that converts the optical image formedby the zoom lens system into the electric image signal, wherein the zoomlens system comprises a plurality of lens units each composed of atleast one lens element, in which an interval between at least any twolens units among the lens units is changed so that an optical image ofan object is formed with a continuously variable magnification, a firstlens unit arranged on the most object side among the lens units includesa lens element having a reflecting surface for bending a light beam fromthe object, and has negative optical power, and any one of the lensunits, any one of the lens elements, or alternatively a plurality ofadjacent lens elements that constitute one lens unit move in a directionperpendicular to an optical axis.